1660s, "the structure of a machine, engine, or other contrivance for controlling or utilizing natural forces," from Modern Latin mechanismus, from Greek mēkhanē "machine, instrument, device" (see machine (n.)). Sense of "a mechanical contrivance or agency of any kind" is from 1670s.
"making revolutions, rotating," 1690s, present-participle adjective from revolve (v.). Revolving door is attested from 1856 in industrial processes, 1896 in buildings.
1873, an irregular shortening of rotator, originally in mathematics. Mechanical sense of "rotating part of a motor" is attested by 1903; specifically of helicopters from 1930.